On 12/4/2013 10:44 AM, Warren Young wrote: > Bottom line: 70% is too impure for this task. Huh?!? I've cleaned numerous CPU-heatsink surfaces with 70% isopropyl, never had any problem.... heck, I clean optical lenses with it, in the form of those eyeglass wipes you buy by the crate at Costco. in tests we did 30 something years ago, the 90% medical stuff left a white haze, while the 70% regular rubbing stuff didn't. we were using it for cleaning the heads and tape paths of 9 track computer tape drives. sure, the analytic laboratory grade was clean, but also stupid expensive, as we were going through a quart a week cleaning a dozen high speed tape drives 3 shifts a day 6 days a week (they were in constant use loading tapes shipped to us from vendors, so got rather dirty rather fast). -- john r pierce 37N 122W somewhere on the middle of the left coast